| Author |
 Topic Search  Topic Options
|
MarkM5 
Newbie
Joined: 20-December-2002
Location: United Kingdom
Status: Offline
Points: 5
|
 Topic: Bypass
Posted: 20-December-2002 at 18:40 |
Hi I own an 1990 M5 and was thinking of removing the cat as it's not reqired for mot at this age, has anyone done this before? are there any advantages/disadvantages?Also my car seems to run very rich the tailpipes get very sooty and it starts to misfire in traffic until you get to open her up when it clears it also showed 9.7MPG on the computer!! any help would be greatly appreciated.
Merry Christmas
|
 |
|
Sponsored Links
|
|
|
Guests
Guest
|
Posted: 26-December-2002 at 16:53 |
Mark,
I run a 3.8 without cat - I have a simple twin pipe straight through to the rest of the exhaust. The rest of the emissions hardware is still in place, which means you must accommodate the Oxygen sensor somewhere. In other words, my car's brain still "thinks" the cat is fitted. It runs fine - idle is a little more lumpy due to the lower back pressure, but other than that it's great. Sounds better too.......
Your MPG sounds awful, unless it's all slow town driving - what does your car return on a normal run? It may be best to calculate from what you put in than trust the OBC - they can sometimes tell fibs.
Misfires - best to look at the obvious first. Plugs, leads and dizzy cap are the most likely culprits. Poor electrics could also affect your MPG, especially if you have to use the throttle lots to clear the problem.
|
|
MarkM5
Newbie
Joined: 20-December-2002
Location: United Kingdom
Status: Offline
Points: 5
|
Posted: 27-December-2002 at 22:22 |
Does removing the cat make it much noisier?
Apart from removing the cat have you done anything else to your car?
As far as the misfire’s concerned it seems to be more on the fuelling side as if it’s getting to much and chocking the engine, it’s only happened once when I was stuck in traffic for about an hour, also on full throttle you get brown smoke out the back not an excessive amount but very visible, anyway I’ll check all the things you suggested and let you know if anything turns up.
Thanks Kurt
Mark
|
|
frank
Senior Member I
Joined: 13-November-2002
Location: United Kingdom
Status: Offline
Points: 105
|
Posted: 27-December-2002 at 22:45 |
I also get smoke / vapour on hard acceleration and have sooty tail pipes. Hasnt been checked by thme but BMW said could be moisture build up in the cat which isnt cleared out by normal running.
My mpg is around 18mpg though.
1992 M5 3.8
|
|
IamSpartacus
Moderator Group
Joined: 21-November-2002
Location: Singapore
Status: Offline
Points: 3625
|
Posted: 06-January-2003 at 16:48 |
I also get smoke / vapour on very hard acceleration but don't have the sooty tail pipes... My average mpg is around 19 - 20mpg so I must behaving better than I thought!! Mines a 1994 M5 3.8 with 115,00 clocked up - the last 2K in the last fortnight!
|
|
The world is a tragedy to those who feel, but a comedy to those who think.
|
|
Guests
Guest
|
Posted: 06-January-2003 at 21:03 |
Mark,
Cat removal makes a only slight difference to volume, and improves the quality of the noise. It is not at all intrusive. Other than that the car is standard.
How's the misfire ?
|
|
stevie53
Really Senior Member II
Joined: 14-January-2003
Status: Offline
Points: 2486
|
Posted: 14-January-2003 at 14:08 |
Derek
my car having covered 125,000 has the same characteristics as your car except I have the sooty tail pipes. I find that the car is running fine so I don't want to pry too deep (if it's not broken don't fix it)
|
|
///2000 E39 M5 Imola Red/// NO MORE
una volta lei ha avuto l'italiano lei non andrà mai tedesco di nuovo haha
|
|
IamSpartacus
Moderator Group
Joined: 21-November-2002
Location: Singapore
Status: Offline
Points: 3625
|
Posted: 15-January-2003 at 13:14 |
|
I have taken that approach with my cars in the past, not prepared to take this risk on the M car though. Mines far from being the best example out there but I don't want it getting any worse.
|
|
The world is a tragedy to those who feel, but a comedy to those who think.
|
|
Bypass